Acidithiobacillus ferroxidans was used to oxidize Fe2+ into Fe3+ in the ferrisulfas liquor

and then dissolved Fe3+ was reduced by H2S

achieving both reclamation of the liquor and removal of H2S. The key factor for the removal efficiency of this treatment system was high concentration of dissolved Fe3+. However

when NH4+ and K+ were excessive

most portions of dissolved Fe3+ would be transferred into Jarosite. The nitrogen source was optimized to obtain high concentration of Fe3+ by controlling its ingredients and concentrations. It showed that (NH4)2HPO4 could replace (NH4)2SO4 to be the nitrogen source and its concentration in 0.33-1 g·L-1 was a suitable range for cell growth of Acidithiobacillus ferroxidans. At 1 g·L-1

the bacterial growth did not exhibit obvious lag period; average oxidation rate of Fe2+ was 0.221-0.229 g·(L·h)-1

dissolved Fe3+ increased to 7.62-7.72 g·L-1

and precipitation was 1.17 g·L-1. Therefore

the optimal concentration of (NH4)2HPO4 was 1 g·L-1. In order to reduce cost

the concentration was lowered 0.33 g·L-1. This technique not only maintained the Fe2+ oxidative activity of Acidithiobacillus ferroxidans but also effectively increased dissolved Fe3+ produced during bacterial culture process

providing scientific optimization basis for removal of H2S by the ferrisulfas liquor.